Up: Early 3.0L Vulcan with distributor. Why? Swappable performance parts (i.e. 5.0L valvetrain parts) and you can basically take the existing harness and distributor and swap in. Drawback is tranny swap as well.

Down: 2.3L Gas/turbocharged or 2.3L Diesel. Both can be low-buck big-bang setups.

Extreme: 289/302/351W coupled with either TFI or Duraspark and Fuel injection. Might be a wiring harness nightmare, but if you're going that extreme, I'm sure extreme disassembly is going to be part of the picture

 

It's all in what you are planing to do. I go out if the florida glads and that mud get deep and thick. But the rig does not run as well up north in the mountains becouse it's not set up for that..

 

I'd go for a 302 w/351c or svo heads. Or a 900hp 2.3 but there goes any mileage

 

Eh, trim away a few inches (OK feet) of firewall and slide a 300 I-6 in w/a T-18. Tons of torque, the trans has a granny gear built in as well as being a very durable trans, and the 300 is unbeatable for durability. But for the trouble, I really like the 2.3l idea, find me any engine as solidly built as a 2.3l! And between racer-walsh and esslinger, you can get as many ponies as you are willing to buy! On the diesel front, why not snag a Cummins 3.4l I-4, or a small Cat? The possiblilities are limitless, and as varried as the people presenting them. And I have to go with EFI for wheeling, any time you get over 45 degrees off level, you'll wish you had something with no float!!!